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1.
Hg0 absorption in potassium persulfate solution 总被引：1，自引：0，他引：1
The aqueous phase oxidation of gaseous elemental mercury （Hg^0） by potassium persulfate （KPS） catalyzed by Ag^＋ was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption （CVAA） and ion chromatograph （IC）, respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate （SN）, temperature, Hg^0 concentration in the reactor inlet and tertiary butanol （TBA）, free radical scavenger, on the removal efficiency of Hg^0 were studied. The results showed that the removal efficiency of Hg^0 increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg^0 was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO3. High Hg^0 concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed. 相似文献
2.
Study on oxidizing cellulose to 2.3-dialdehyde cellulose by sodium periodate （NalO4） was carried out. The effects of reaction conditions such as pH of solution, temperature, oxidant concentration, oxidation time. the particle size of 2,3-dialdehyde cellulose and alkali treatment temperature on the dialdehyde concentration ot cellulose were investigated in detail, The results show that the aldehyde group content was created while reaction temperature and alkali treatment temperature increased. The most principal factors affecting the aldehyde group content of 2,3-dialdehyde cellulose were found out and the best oxidation conditions were as follows： the pH was 2. the reaction temperature was 45℃. the mass ratio of cellulose to NalO4 was 1/2, the reaction time was 4 h, the alkali treatment temperature was 70℃ and smaller particle size was 0.80 mm. 相似文献
3.
Active Fe-and Mn-loaded MCM-41(Fe–Mn/MCM-41),which was synthesized via a hydrothermal reaction followed by impregnation,is used in the heterogeneous Fenton reaction to degrade methyl orange(MO) in aqueous solution. The synthesized samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,N_2 adsorption–desorption isotherm analysis,Fourier transform infrared spectroscopy,and X-ray photoelectron spectroscopy. Compared with Fe/MCM-41 and Mn/MCM-41,Fe–Mn/MCM-41 showed higher activity for MO degradation and mineralization. Effects of various operating parameters,such as pH,Mn content,and H_2O_2 dosage,on the degradation process were subsequently investigated. Results of experiments on the effect of radical scavengers revealed that the degradation of MO could be attributed to oxidation by HO_·. The synergy of Fe and Mn species in the Fenton oxidation process was also explained. 相似文献
4.
Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one. 相似文献
5.
In this study, liquid-phase aerobic oxidation of toluene catalyzed by Mn–Mo oxide was conducted in a 1.0 L batch reactor. The macroscopic kinetics of toluene consumption and benzaldehyde generation at 413–443 K were obtained from a combination of experimental observation and hypothetical models. The results clearly showed that both the oxidation rate of toluene and generation rate of the aromatic product were proportional to the concentration of the substrate, the partial pressure of oxygen and the surface area of the catalyst. The energy barrier of toluene oxidation to benzyl alcohol was the highest(≈ 81 kJ mol~(-1)), while that of benzyl alcohol oxidation to benzaldehyde was the lowest(≈ 57 kJ mol~(-1)). Moreover, the activation energy of further oxidation of benzaldehyde in an acetic acid solvent was only slightly lower(≈ 1.9 kJ mol~(-1)) than that of toluene oxidation. Significantly, the transformation of benzyl alcohol indeed contributed to the generation of benzaldehyde and this step conformed to a first-order parallel-consecutive model. Increased reaction temperature and residence time favored the transformation of benzyl alcohol to benzaldehyde. In addition, doping with molybdenum at Mn/Mo = 3/1 enhanced the catalytic performance of the heterogeneous catalyst and was attributed to the presence of a synergetic effect between different metal cations. Regarding the microscopic kinetics, the LH-OS-ND mechanism(Langmuir–Hinshelwood adsorption of reagents on the same type of active sites and non-dissociative adsorption of oxygen) was verified as responsible for the heterogeneous oxidation of toluene. Oxygen and benzaldehyde were weakly adsorbed(Δ H_(ads,Oxy) ≈~(-1)5 kJ mol~(-1), Δ H _(ads)0,Bald) ≈-30 kJ mol~(-1)), but showed strong mobility(Δ S_(ads,Oxy) ≈-22 J mol~(-1) K~(-1)), Δ S_(ads,Bald) ≈-39 J mol~(-1) K~(-1)). The fundamental intrinsic rates were deduced based on the LH-OS-ND mechanism and showed great consistency with the macroscopic results. 相似文献
6.
The extractive reaction process of oxygen-working solution-water three-phase system for the production of hydrogen peroxide by the anthraquinone method was investigated in a sieve plate column of 50 mm in internal diameter. The oxidation reaction of anthrahydroquinone in the working solution with oxygen and the extraction of hydrogen peroxide from the working solution into aqueous phase occurred simultaneously in the countercurrent mode. The agitating effect caused by gaseous phase made the droplets of the dispersed phase become smaller, thus, increasing the liquid-liquid interfacial contact areas and resulting in the improvement of the mass transfer velocity. Results showed that the gas-agitation had a beneficial effect on the extraction of hydrogen peroxide from the working solution into the aqueous phase： the concentration of hydrogen peroxide in the raffinate decreased with the increase of the gaseous superficial velocities： and the concentration of H2O2 in the raffinate increased with the increase of the dispersed phase superficial velocity at the same superficial velocity of the gaseous phase. In the G-L-L extractive reaction process, with the increase of the gaseous superficial velocities, both the conversion of the anthrahydroquinone oxidation and the extraction efficiency of hydrogen peroxide first increased significantly, then increased gradually. 相似文献
7.
Natural pyrites contain high levels of adsorbed and structurally incorporated arsenic(As),which may simultaneously result in the release of As and affect the oxidation process of pyrite.However,the oxidation and electrochemical behaviors of As on the oxidation reactivity of pyrites are still not clear.In this study,pyrite was prepared by a hydrothermal method and applied to study the oxidation mechanism between pyrite and aqueous arsenate.Analyses of X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy demonstrate that the as-prepared sample is an octahedron-like pyrite with high purity and crystallinity.The interaction between As(V)and pyrite as well as the electrochemical behaviors of pyrite oxidation in the presence of aqueous arsenate were investigated under acidic conditions by an ion analysis method,cyclic voltammetry(CV),Tafel,and electrochemical impedance spectroscopy(EIS).The results of the chemical reaction indicate that electrons are transferred from S _2~(2-)to dissolved oxygen with the formation of SO _4~(2-)in the initial As(V)concentration range of 0–0.3 mmol/L.In the initial As(V)concentration range of 0.4–1.2 mmol/L,electrons are transferred from S _2~(2-)to As(V)with the formation of elemental S ~(0 )and As(III).The CV,the Tafel plot and EIS analyses indicate that aqueous arsenate in an electrolyte promotes oxidation reactivity and passivation of the pyrite electrode.Moreover,the electron transfer rate increases with increasing aqueous arsenate concentration in the electrolyte. 相似文献
8.
In this paper, 2,3,5-trimethyl-1,4-benzoquinone(TMBQ) was synthesized through the direct oxidation of1,2,4-trimethylbenzene(pseudocumene, TMB) in the HCOOH–H_2O_2 system. The influence ofthree active species was studied, including performic acid(PFA) generated in formic acid, peracetic acid(PAA) generated in acetic acid, and trifluoroperacetic(TFPA) acid generated in trifluoroacetic acid. The effects ofsulfuric acid and sodium formate addition were investigated, the overoxidation ofTMB was discussed, and the main reason for the decreasing selectivity was revealed. The oxidation ofTMB can be controlled and improved through adjusting the reaction temperature, mole ratio ofoxidant to substrate, and reactant concentration. The TMBQ yield of28% was achieved with a TMB concentration of0.2 mol/L, H_2O_2/TMB mole ratio of6:1, and reaction temperature 37 °C. The selectivity of72% was obtained with a TMB concentration of0.2 mol/L, H_2O_2/TMB mole ratio of5:1, and reaction temperature of27 °C. The reaction mechanisms were proposed and discussed based on the gas chromatography–flame ionization detection(GC–FID) and gas chromatography–mass spectrometer(GC–MS) results. 相似文献
9.
The urea nitrogen adsorbent of complex type, which consists of chitosan coated dialdehyde cellulose （CDAC） and immobilized urease in gelatin membrane （IE）, was prepared. The cellulose, the dialdehyde cellulose （DAC） and the CDAC were characterized by scanning electronic microscope. The results indicate that the cellulose C2-C3 bond was broken under the oxidation of periodate and it was oxidated to DAC. The DAC was coated with chitosan and the CDAC was obtained. The adsorption of urea nitrogen onto the adsorbent in Na2HPO4-NaH2PO4 buffer solution was studied in batch system. The effects of the experiment parameters, including degree of oxidation of CDAC, initial urea nitrogen concentration, pH and temperature, on the adsorption capacity of urea nitrogen onto the adsorbent at CDAC/IE weight ratio 10：1 were investigated. The results indicate that these parameters affected significantly the adsorption capacity. The adsorption capacity of urea nitrogen onto the adsorbent was 36.7 mg/g at the degree of oxidation of CDAC 88%, initial urea nitrogen concentration 600 mg/L, pH 7.4 and temperature 37℃. 相似文献
10.
Aspergillus oryzae 3042 mycelium pellets were immobilized by crosslinking method with reagents of gelatin and formaldehyde. An orthogonal design table was used to determine the optimal immobilization conditions. The L-aminoacylase activity of immobilized mycelium pellets under optimal conditions was assayed. The results show that the L-aminoacylase activity was 1 350 U·g-1. and the activity retention rate was 83%. The properties of the immobilized preparation were studied. Compared with free pellets, the appropriate pH of reaction system changed from 7.0 to 8.0, temperature changed from 52℃to 63℃, and the ranges of the optimum reaction conditions were all improved. The effect of Co2 on immobilized mycelium pellets was investigated and the favorable concentration was determined. When the immobilized preparation was used for the resolution of D, L-alanine in a packed bed reactor with 10 mm in diameter, 200 mm in height, the operational stability was increased, and the half-life period was 53 d. Thermal stability analysis shows that the immobilized pellets were more stable than the free pellets. 相似文献
11.
Long lasting strontium aluminate phosphors were synthesized by means of coated precipitation in the experiment. SrA12O4 monoclinic phase with long afterglow was synthesized at 1 100 ℃ with the aid of H3BO3,and the synthetic temperature decreased about 100 ℃-150 ℃ than in solid state reaction. The process of heat treatment was studied by TG-DTA. The phase compositions of powders were analyzed by XRD. The micrographs of the samples were investigated by SEM and the luminescent properties were researched by optical spectrum. The effects of H3 BO3 on the phase composition and microstructure of the calcined powders were investigated. The results indicated that H3BO3 accelerated the formation of SrAl2O4 by consuming the intermediate phase. The addition of Dy2O3 stimulated the afterglow property due to the increase in the depth of the trap center in the materials. 相似文献
12.
The solubilities of 2-naphthalenesulfonic acid monohydrate and sodium 2-naphthalenesulfonate in sulfuric acid solutions were measured at temperatures ranging from 278.15 to 338.15 K by using a dynamic method. The concentration of sulfuric acid solution ranged from 0 to 80wt%,. The solubilities of 2-naphthalenesulfonic acid monohydrate and sodium 2-naphthalenesulfonate increased with temperature, and both of them were the lowest at 70wt %, of sulfuric acid solution(w~0_3 =0.70)while the highest in pure water. The solubility data were correlated by the modified Apelblat equation. Based on the solubility difference between 2-naphthalenesulfonic acid monohydrate and sodium 2-naphthalenesulfonate, a new technique in which sodium sulfate was used to replace sodium sulfite in the neutralization reaction was developed. The suitable mole ratio of H_2O to Na_2SO_4 in the neutralization reaction was 80∶1, and that of 2-naphthalenesulfonic acid monohydrate to Na_2SO_4 was 3.2∶1. The material balance under the suitable mole ratios was given and discussed. 相似文献
13.
In order to clarify the equilibrium components in the hydrolysis solution of boron trifluoride(BF_3-H_2O),the BF_3-H_2O was prepared by mixing BF_3-CH_3OH with large amount of water,in which the stoichiometric concentration of BF_3 is less than 0.1 mol/L.Two ionic equilibrium models were proposed to simulate the hydrolysis equilibrium of BF_3 and tested by special acid-base titration technique.The most accurate ion equilibrium constants were determined.The model,which was assumed to have no HF,was proved to be more representative for the real system and used to simulate the hydrolysis equilibrium of BF_3.The simulation suggested that H~+,BF_4~-,BF_3OH~- and H_3BO_3 were the main species in the dilute hydrolysis solution,while BF_2(OH)_2~- and F~- were insignificant species whose concentrations were both in the order of 10~(-4) mol/L magnitude,and BF(OH)_3~- could be omitted because its concentration almost equaled zero.Meanwhile,the equilibrium constant of the overall ionic reaction at 25℃ was obtained as 161.6. 相似文献
14.
C.I. Acid Red 73(AR73)wastewater was treated by cross-flow nanofiltration coupling electro-catalytic oxidation using an NF90 membrane and a Ti/SnO_2–Sb anode prepared via electrodeposition.Experiments conducted for standard electrochemical degradation of AR73 studied the reaction rate ofremoving AR73 using the Ti/SnO _2–Sb anode.A computational fluid dynamics(CFD)model was developed to predict the permeate flux under a laminar flow regime,including the effects ofoperating pressure,applied potential,initial concentration,and cross-flow velocity on this coupling process.The variations of the membrane surface concentration and permeate flux along the length of the channel were quantified.The experimental results were compared with those predicted by the model,and they agreed well. 相似文献
15.
Huan Wang Dong-mei Liu Zhi-wei Zhao Fu-yi Cui Qi Zhu Tong-mian Liu 《浙江大学学报(A卷英文版)》2010,11(2):143-150
The formation of brominated trihalomethanes （THMs-Br） which is proved more carcinogenic than their chlorinated analogues reported was very different at various water qualities. This study was performed to assess the effects of water quality parameters （bromide concentration, pH value and ammonia concentration）, chlorination conditions （chlorine dose, reaction time） and ratios of Br^-/DOC and Br^-/Cl2 consumption on the formation and distribution of THMs-Br in chlorination. The results showed good correlation between the bromine incorporation factor （BIF） n（Br） and Br^-/Cl2 consumption ratio. The formation of total THM （TTHM） was found to＇ decrease with increasing ammonia concentration but to increase with bromide concentration and pH value. The n（Br） trends were significantly affected by the presence of bromide concentration. The effects on the molar yields of THMs were more strongly influenced by bromide concentration and dissolved organic carbon （DOC） concentration than pH value and natural organic matter （NOM） source. High Br^-/DOC and Br^-/Cl2 favor the formation of THMs-Br over chlorinated THMs （THMs-Cl）. The experimental data including the main parameters such as bromide, DOC, ammonia, pH and reaction time were used for developing the predictive model for THMs-Br. 相似文献
16.
《天津大学学报(英文版)》2016,(2)
The relation of boron trifluoride concentration with conductivity in boron trifluoride methanol solution(BF_3-CH_3OH)was power exponent fitted in low concentration range. The kinetics of the reaction between boron trifluoride methanol complex and sodium methoxide to produce enriched ~(10)B methylborate was proposed based on a detailed mechanism study, and was verified by acid-base titration method and conductivity method. It was found that this reaction is first order reaction and the rate constant is 0.022 min~(-1) at 338 K(65 ℃), the activity energy is 65 k J/mol. In addition, it was found that the conductivity method is more feasible to measure the kinetic curve than acid-base titration method. 相似文献
17.
WANG Fang CHENG Shui-yuan LI Ming-jun FAN Qing CHEN Dong-sheng WANG Hai-yan ZHANG Wei 《重庆大学学报(英文版)》2010,9(3):117-123
We developed and tested an improved neural network to predict the average concentration of PM10 （particulate matter with diameter smaller than 10 μm） several hours in advance in summer in Beijing. A genetic algorithm optimization procedure for optimizing initial weights and thresholds of the neural network was also evaluated. This research was based upon the PM10 data from seven monitoring sites in Beijing urban region and meteorological observation data, which were recorded every 3 h during summer of 2002. Two neural network models were developed. Model I was built for predicting PM10 concentrations 3 h in advance while Model II for one day in advance. The predictions of both models were found to be consistent with observations. Percent errors in forecasting the numerical value were about 20%. This brings us to the conclusion that short-term fluctuations of PM10 concentrations in Beijing urban region in summer are to a large extent driven by meteorological conditions. Moreover, the predicted results of Model II were compared with the ones provided by the Models-3 Community Multiscale Air Quality （CMAQ） modeling system. The mean relative errors of both models were 0.21 and 0.26, respectively. The performance of the neural network model was similar to numerical models, when applied to short-time prediction of PM10 concentration. 相似文献
18.
Raw corn starch granules were hydrolysized by glucoamylase in a chemostat. The hydrolysis of three different-sized granules shows that smaller granules undergo more hydrolyzation than larger ones. After 78 h, 97% of the granules was hydrolysized with diameter between 0.15 mm and 0.3 mm at 50℃. When corn starch concentration increased from 100 g/L to 250 g/L, the amount of reducing sugar produced was proportional to the initial substrate concentration and no substrate inhibition phenomenon appeared. In order to study the product inhibition exactly, the product from hydrolysis reaction itself was added into the hydrolysis system at the beginning of starch hydrolysis.Product inhibition with different quantities of product added were studied in the initial several hours,during which period enzyme inactivation could be neglected and product inhibition could be studied separately. The experiments indicate that product inhibition happens when the additional quantity exceeds 9.56 g/L. 相似文献
19.
Fe (Ⅲ)-catalyzed ozonation yielded better degradation rate and extent of COD (Chemical Oxygen Demand) or oxalic acid as compared with oxidation by ozone alone. Two parameters with strong effects on the efficiency of ozonation are pH of the solution and the catalyst (Fe3 ) dosage. The existence of a critical pH value determining the catalysis of Fe (Ⅲ) in acid conditions was observed in phenol and oxalic acid systems. The best efficiency of catalysis was obtained at a moderate concentration of the catalyst. A reasonable mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol was obtained based on the results and literature. 相似文献
20.
A low-cost and easily prepared manganese carbonate(Mn CO_3) has been synthesized for catalytic conversion of 5-hydroxymethylfurfural(5-HMF) to 2,5-diformylfuran(DFF). The properties and morphology of the manganese carbonate were measured by SEM,XRD,TGA,BET and XPS. In this method,no harsh reaction conditions were required,and it was a simple and green process for the oxidation of 5-HMF into DFF. To achieve an optimum DFF yield,different reaction conditions,including reaction temperature,reaction time,catalyst amount,and solvents were investigated. Results from the experiments indicated that the highest DFF yield of 86.9% was obtained at 120 °C under atmospheric oxygen pressure after 6h. Finally,Mn CO_3 could be used at least five times with considerable stability. 相似文献